FinFET Dielectric Isolation via Flowable Oxide and Stressor
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Solution Overview
Problem
Bulk finFETs face challenges with leakage currents and device variability due to lack of effective isolation, leading to degraded electrical performance and increased manufacturing costs compared to silicon-on-insulator (SOI) finFETs.
Innovation Solution
A method involving a sacrificial layer and stressor regions is used to form a semiconductor structure with an insulator region replacing the sacrificial layer, enhancing carrier mobility and isolation without introducing dopants, comprising a bulk semiconductor substrate, a top silicon region, and a stressor region with a specific germanium content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bulk finFET structure is used to reduce manufacturing cost, then manufacturing cost is reduced, but leakage currents and device variability increase
Solution Approach 1:
The substrate is segmented into isolated regions using insulator regions formed between adjacent fins, creating electrically isolated islands that prevent leakage currents while maintaining the bulk substrate structure for cost-effectiveness
Solution Approach 2:
An insulator region acts as an intermediary material between the semiconductor substrate and the top silicon region, providing electrical isolation to eliminate leakage paths while allowing the bulk finFET structure to be maintained
2Reliability
If insulator region is added to reduce leakage currents, then leakage currents are reduced, but device complexity increases
Solution Approach 1:
The insulator region formation is merged with the existing finFET fabrication process steps, including using the same sacrificial layer removal process and combining stressor region formation with the isolation structure creation, thereby reducing overall process complexity
3Reliability
If stressor region with germanium content is introduced to improve carrier mobility, then carrier mobility is improved, but manufacturing precision requirements increase
Solution Approach 1:
The germanium content in the stressor region is optimized to a specific range (40-50%) to achieve the desired stress effect and carrier mobility improvement while maintaining manufacturability and avoiding excessive precision requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves carrier mobility and reduces device variability, achieving better electrical performance and lower manufacturing costs by providing effective isolation and stressor regions below the top level of the bulk substrate.
Implementation Method 1
a stressor region disposed adjacent to the metal gate and recessed below a top level of the semiconductor substrate
Data Source
AI summary
A finFET and method of fabrication are disclosed. A sacrificial layer is formed on a bulk semiconductor substrate. A top semiconductor layer (such as silicon) is disposed on the sacrificial layer. The bulk semiconductor substrate is recessed in the area adjacent to the transistor gate and a stressor layer is formed in the recessed area. The sacrificial layer is selectively removed and replaced with an insulator, such as a flowable oxide. The insulator provides isolation between the transistor channel and the bulk substrate without the use of dopants.